Engineering Construction

Engineering Construction Division (ECD) which has a very significant presence in the nuclear sector, is an important business vertical of Avasarala providing services. ECD has taken a wide spectrum of projects ranging from critical and quality intensive programs like reactor life extension to quantity intensive supply and erection programs like cable tray installation projects.

We have the unique distinction of undertaking projects in radiation environment with several records to our credit for containing the radioactive dosage level to the lowest through very effective automation.

 

EPC services:

  • Field support for life extension programmes (Enmasse Coolant channel replacement).
  • Installation and professional site services.

On site services:

  • New power plant installation services and refurbishment of old power plants.
  • Coolant Channel Assembly
  • Installation of
    • Reactivity Mechanisms.
    • Fuel handling Equipments – Column/Bridge.
    • Calandria & End Shield.
    • Fuel Transfer Equipment.

Projects undertaken:

CALANDRIA AND END SHIELD INSTALLATION:

A site work executed during a 220MWe nuclear power plant construction. Installation involved 1 No. Calandria, 2 Nos. End shields, 1No. Ion chamber, filling of steel balls in end shields, liner work inside calandria vault.

 

Fabrication of special lifting tools and tackles, load test certification prior to using was part of work.

 

Criticalities:

  • Handling of heavy (110 Tonnes) large sized (5.5 meter diameter) end shields and calandria.
  • Installation with high level of accuracy  in position and alignment.
  • Filling of steel balls inside end shields to prescribed volumetric norms.
  • Systematic stainless steel welding in site ensuring specified optical alignment accuracy.
  • Welding by qualified welders using certified weld consumables.
  • Stringent non-destructive weld test to withstand radiation level of more than 1000 Rems/hour inside calandria.

The installation was completed by engineers and technicians in a record time of 44 weeks. Seamless coordination with various agencies adhering to the elementalised time schedule was the essence of the execution of work.

 

REACTIVITY CONTROL MECHANISM:

Employed for controlling and regulating reactivity level inside calandria of 220 MWe reactor. Functions include Drive – In and Drive –Out of the neutron absorbing elements in the reactor core. Works on the principle of winding of rope over sheave using a controlled electric motor. The Unique feature is minimizing of wear particles due to rubbing / rolling of metal to metal parts thus reducing reactor contamination particularity of undesirable element.

 

Criticalities

  • Directly mounted on calandria in vault with 10-15 Rems/hours radiation level.
  • Performs at a speed of 18mm/sec uninterruptedly where lubrication is prohibited.
  • Have interchangeability for spares and replacements .
  • Works directly facing active heavy water having 100 Rems/hour radiation level at 65oC temperature.
  • Safety mechanism against uncontrolled reactivity levels.

Execution of this involved modelling and preparation of engineering drawings from concept design. Extensive planning and engineering, establishing intricate stainless steel castings, forgings. Machining carried out in separate cells to ensure non-contamination of carbon steel. Assembly and cold run tests to demonstrate 30 million cycles at various working simulated parameters executed by setting up a 15 meters high working platform. Actual flow at elevated temperature simulated to ensure fault free working. The unit is installed and commissioned at site.

 

EN MASSE COOLENT REPLACEMENT

As the reactors reach an end of life, its life is further enhanced by carrying out the critical re-furbishing work which ensures and extends the life of the reactor. This work is carried out during the typical shutdown period which consists of replacement of all Coolant Channel items and installation of new pressure tubes and associated items. The Work is carried out in a radiation environment with a dosage rate varying between 250 milli–Rems/hour to 100 milli-Rems/hour. A manpower intensive campaign involving minute planning, scheduling & training of skilled operators with critical monitoring of the allowable radiation dosage. Testing prior to hand over inspection and recording of measurements. Norms prescribed by AERB are applicable.

 

Criticalities

  • Adherence /Expected Improvements in time schedule.
  • Limiting dosage with in estimates.
  • Optimum utilisation of man power.
  • Elaborate site management techniques to meet non-stop work execution.

Innovative powered automation devices introduced to reduce radiation exposure and to improve productivity. Extensive training of operators in a full scale mock set-up adapted. The cumulative radiation dosage of 575 man-Rems was achieved. The work was completed in 10 months. The expertise gained has resulted in achieving successful repeat performance in other locations and projects.

 

Engineering Procurement and Construction – EPC is a part of Avasarala Group, which specializes in taking up various works in the Nuclear Island.

  • Installation of Equipments for New Builds
  • Piping Works
  • Life Extension work for Nuclear Power Plants

 

WORKS CARRIED OUT FOR NEW BUILDS

 

Coolant Channel Installation

   
  • No of Coolant channel per Reactor- 392 / 306.
  • Thorough surface preparation to Nuclear standards.
  • One side pre-rolling , in situ second side rolling & Welding.
  • Shrink fit operation & baroscopic tests.
  • Vacuum Leak checking using helium leak detector.
  • Annular Gas Monitoring & Inspection.
  • Work carried out for TAPP, RAPP & KAIGA, Nuclear Power Plants.

 

CALANDRIA & END SHIELD INSTALLATION

   
  • Size:5.5 meter.
  • Weight:110 Tonnes.
  • Height of lifting : 32 meters.
  • Mobile Crane used : 640 Tonnes.
  • Validation of lifting devices.
  • Precision installation & Alignment.
  • Sequential welding of by qualified welders.
  • Simultaneous working in both Vaults.
  • Validation through optical instruments.
  • Zero defect execution.
  • CS Ball filling of 45 tonnes & Radiometry test.
  • Work carried out for RAPP Power.

 

INSTALLATION OF REACTIVITY CONTROL MECHANISM

   
  • Mock up for validation.
  • Thorough surface preparation as per Nuclear grade standards.
  • Main assembly dismantling.
  • Material handling, Installation, Alignment checking using  transit optical instruments.
  • Interface welding to Calandria & Alignment checking.

 

LIFE EXTENSION WORKS ON EXISTING REACTORS

 

EN-MASSE COOLANT CHANNEL REPLACEMENT

   
  • Total Manrem allocated  1,200.
  • Manrem consumed  575.;
  • Duration 8 Months.
  • No. of workmen employed  1,250.
  • Set a World Record for CANDU type.

Avasarala’s Unique approach in executing the job

  • Well screened manpower.
  • Mock up trials, Training & Qualification.
  • Automating critical processes.
  • Adherence to Safety.
  • Extensive Quality Documentation.
  • Work Carried out for MAPS, NAPS & KAPS Power Plants.

 

EN-MASSE FEEDER REPLACEMENT

   
  • No of Feeder Pipe replaced -  306.
  • Thorough surface preparation to Nuclear standards.
  • Onsite Fabrication of Feeder Pipes, Mock up & Installation.
  • Critical Pipe bending.
  • Healium Leak Testing after installation.
  • Works carried out for NAPS & RAPS Power Plants.

 

WORKS CARRIED OUT BHAVINI FAST BREEDER REACTORS

 

  • Temporary Sodium Transfer System.
  • Cable Tray Works.
  • Top Shield Argon System.
  • Effluent Treatment System.
  • Storage Pit for Slender Components.
  • Complimentary Shielding Boxes.
  • Fresh Fuel Transfer Cask.
  • Supply & Installation of Heating Cables.
  • Lead Shielding for Sodium & Liquid Effluent Tanks.